body {
  gap: 18px;
  user-select: none;
  -webkit-user-select: none;
  touch-action: none;
}
h1 { font-weight: 700; font-size: 2.6rem; }
.top {
  display: flex;
  align-items: center;
  gap: 14px;
  width: 360px;
  max-width: 92vw;
}
.scores { display: flex; gap: 10px; margin-left: auto; }
#board {
  position: relative;
  width: 360px;
  height: 360px;
  max-width: 92vw;
  background: var(--surface);
  border-radius: 12px;
  padding: 10px;
  box-shadow: 0 10px 40px var(--shadow);
}
.grid-bg {
  position: absolute;
  inset: 10px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(4, 1fr);
  gap: 10px;
}
.grid-bg div { background: var(--surface-2); border-radius: 8px; }
#tiles { position: absolute; inset: 10px; }
.tile {
  position: absolute;
  width: var(--ts);
  height: var(--ts);
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1.8rem;
  transition: transform 0.12s ease;
  background: #3a4a7a;
  color: #fff;
}
.tile.pop { animation: pop 0.16s ease; }
.tile.new { animation: appear 0.16s ease; }
@keyframes pop { 0%{transform:var(--pos) scale(1);} 50%{transform:var(--pos) scale(1.15);} 100%{transform:var(--pos) scale(1);} }
@keyframes appear { 0%{transform:var(--pos) scale(0);} 100%{transform:var(--pos) scale(1);} }
.t2    { background:#3a4a7a; }
.t4    { background:#46588f; }
.t8    { background:#5d7fd6; }
.t16   { background:#4ecca3; color:#10241c; }
.t32   { background:#3bb389; color:#fff; }
.t64   { background:#e9a445; color:#fff; }
.t128  { background:#e94560; font-size:1.5rem; }
.t256  { background:#d6365a; font-size:1.5rem; }
.t512  { background:#c0245c; font-size:1.5rem; }
.t1024 { background:#ffd460; color:#1a1a2e; font-size:1.2rem; }
.t2048 { background:#ffce00; color:#1a1a2e; font-size:1.2rem; box-shadow:0 0 24px #ffd460; }
.t-big { background:#0f3460; font-size:1.1rem; }
#overlay {
  position: absolute;
  inset: 0;
  background: var(--overlay);
  border-radius: 12px;
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 16px;
  z-index: 10;
}
#overlay.show { display: flex; }
#overlay .msg { font-size: 2rem; font-weight: 700; }
#pad {
  display: grid;
  grid-template-columns: repeat(3, 52px);
  grid-template-rows: repeat(2, 52px);
  gap: 8px;
  justify-content: center;
}
#pad button {
  padding: 0;
  font-size: 1.4rem;
  background: var(--surface);
  color: var(--text);
  border-radius: 10px;
}
#pad button:hover { background: var(--surface-3); opacity: 1; }
.pad-up    { grid-column: 2; grid-row: 1; }
.pad-left  { grid-column: 1; grid-row: 2; }
.pad-down  { grid-column: 2; grid-row: 2; }
.pad-right { grid-column: 3; grid-row: 2; }